Field
The teachings in accordance with the exemplary embodiments of this present disclosure generally relate to headlights having one light source module for a high beam and a low beam, and more particularly to headlights having one light source module for a high beam and a low beam configured to selectively operate a high beam or a low beam by changing a beam having a characteristic of linearly polarized light irradiated from a single light source unit to a circularly polarized light or to an elliptically polarized light, and outputting the beam to one path or two paths in response to a low beam mode or a high beam mode.
Background
A headlight of a vehicle called a head lamp is an illumination light having an essential function of lighting a front path in a night operation, and requires a brightness level capable of ascertaining a traffic obstacle located at a 100 meter ahead of a vehicle in a night operation, albeit there being a difference in terms of performance standard stipulated by each country.
In general, the headlight that lights in order to obtain a front view in a night travel of a vehicle is operated in a high beam (high beam mode) and a low beam (low beam mode), and when the vehicle is operated at a high speed, the vehicle selects a high beam to allow a beam irradiated from the headlight to be directed upwards, whereby a driver can recognize a far-out distance. When the vehicle is operated at a low speed, a low beam is selected to allow the beam irradiated from the headlight to direct downwards to prevent a driver view of an on-coming vehicle or a front vehicle from being obstructed.
To this end, left/right headlights of most vehicles currently consist of two-lighting type headlights with high beam and low beam lights, and commonly use dual filament bulbs, each bulb having a pair of high beam filament bulbs and a pair of low beam filament bulbs. Headlights on medium or higher class vehicles use four-lighting type headlights separately mounted with low beam light bulbs and high beam light bulbs.
The beams emitted from the low beam bulbs and high beam bulbs are reflected by a reflector mirror to be emitted to a front side of a vehicle and illuminate the front side of the vehicle by being adequately distributed.
However, the two-lighting type bulbs suffer from disadvantages in that lighting time is delayed due to repeated change of current between low beam bulbs and high beam bulbs to shorten the life of filaments, whereby a relevant lamp is not lighted when one of the filaments corresponding to the low beam bulbs or the high beam bulbs becomes out of order.
In order to solve the disadvantages thus mentioned, although a laser diode recently researched as one of light sources for headlights has an advantage of sending a beam of high brightness to a farther distance thanks to a smaller light emitting area, the laser diode suffers from various restrictions including a low JT (Junction Temperature, about 100° C.) as a vehicular part that requires reliability of high temperature.
It is therefore essential to constitute respective laser diode modules as many as the number of required light quantities in order to generate required light quantities for low beam bulbs and high beam bulbs respectively. Furthermore, the number of required modules must be minimized in order to save the cost, and to this end, the power applied to the laser diode must be maximally used, which however disadvantageously shortens the life due to increased JT of the laser diode. It is problematic that an inner temperature of a headlight is generally about 100° C., give or take.